U.S. FDA GUIDANCE FOR INDUSTRY

Immunogenicity Assessment for Therapeutic Protein Products

DRAFT GUIDANCE

1. General Comments

General Comment (if any) The use of “aggregate” throughout this document, to refer to the oligomers in the nanometer size range only is confusing. The nomenclature developed at the 2010 Breckinridge meeting, and that was published in the JPS article from the breakout session on this topic should be used instead. In this case aggregate is defined as any self-associated protein species regardless of the size, from dimer to visible particles that are 100’s of micrometers. For specific species the size being discussed should be used (in this case nanometer sized aggregates), or the nanometer size can be defined as oligomers. This terminology went through extensive review by scientists in the field in industry, academia, and the FDA and EMEA, before the article was published, and the field should move to a standard, less ambiguous terminology. There are several statements made based on individual citations which the agency should be careful to state. Some may not be established facts in context of anti-drug immunogenicity.

Add Row(s), if necessary

2. Specific Comments on Text

Line

Section Comment of Person or Company

16 I. INTRODUCTION Footnote 2: The final version of the 2009 draft guidance will be most welcome.

18 – 30

Proposed change to Line 21 “…response to therapeutic proteins or other biologic entitiesRationale: Consideration should be given to other biologic entities such as peptides, gene therapy vectors, etc.

..”

32 - 35 Line 35-36: It will be useful to state that assessment of immunogenicity in non-clinical studies

is out of scope of this guidance.

37 - 41

44 II. BACKGROUND

46 - 60

Lines 52-53: Neutralization of a therapeutic protein, if not endogenous, can frequently be compensated by a higher dose. We recommend that such example be included herein.

62-67

70 III. CLINICAL CONSEQUENCES

72 - 80

Line 72: Suggest changing “frequently results” to “may result” Rationale: Not all classes of TPPs consistently induce frequent

immune responses. As a class, monoclonal antibodies, in general, have not.

Line 74: “life-threatening and catastrophic reactions” are limited to very RARE cases. This should be made clear.

Line 75: Elucidation of an exact mechanism driving an immune response may be difficult in

cases where these are rare or infrequent events. Line 73-74: “ranging from transient antibody responses with no apparent clinical manifestations to life threatening and catastrophic reactions” might imply that transient ADA are harmless and consequently that persistent ADA would be harmful. Such a statement could thus imply that only transient ADA require investigation, whereas the kinetics of ADA formation and its association with clinical consequences must be investigated by sponsors and not assumed because it is possible that transient ADA can also be associated with mild/moderate adverse reactions (e.g., infusion or injection-site reactions) or severe adverse reactions (e.g., hypersensitivity).

82 A. Consequences for Efficacy

84 - 98

Lines 84-85: Like safety consequences, efficacy consequences of immunogenicity can vary, and are unpredictable. Clinical sequelae and neutralization need to be anticipated to be looked for.

Proposed change to Line 89: Remove “(binding)”.

Rationale: All antibodies are binding, whether they are neutralizing or non-neutralizing. Suggest not using this term as a classification category.

Lines 91-95: The description provided here is not exclusive to non-neutralizing. All ADA, whether neutralizing or non-neutralizing, may alter PK.

Lines 96-98: Statement implies that data from neutralizing antibody assays may not be of

clinical utility, and that only correlative data is useful. Line 98: replace the word ‘binding’ with ‘non-neutralizing’ for the same reason described above regarding line 90. Proposed change to line 94: Remove “binding” when referring to antibody.

Rationale: Same comment as above. All antibodies are binding. By classifying antibodies as such, may misinterpret this as a category type.

Proposed change to line 97: “….determine the clinical relevance of both neutralizing and

non-neutralizing antibody responses.” Rationale: Same as above.

100

B. Consequences for Safety

102 - 106

Line 103: The “high index of suspicion” is not defined. Suggest changing to “high risk.”

108

1. Anaphylaxis Comment on Anaphylaxis Section: This section could use more clarity and references to relevant case studies that demonstrate broad TPP implications. It might be helpful to include some of the appendix material here including assay recommendations and assay limitations. Specifically, the limitation of collecting sample in a time frame that would enable meaningful assay results.

Line 108: The title should state “Anaphylaxis and Anaphylactoid reactions” unless the Agency is specifically excluding non-IgE mediated acute (Type 1) hypersensitivity.

110 - 122

Lines 115-117: This statement contradicts the text on Lines 74-77. Measurement/detection of antigen specific IgE is technically challenging and can be confounded by the presence of high levels of therapeutic or anti-therapeutic antibodies of other isotypes (See Lines 1052 – 1060).

Lines 120-122 However, there are major limitations to collection of informative data on

histamine and tryptase - serum samples must be collected in a very short period following the event or they are not informative (see lines 1062-1103). Moreover, accurate detection of product specific IgE is technically challenging and can be confounded by the presence of high levels of therapeutic and/or of anti-therapeutic antibodies of other isotypes (see lines 1052-1060).

124 - 129

Lines 124-129: Determining the underlying mechanism of anaphylaxis is “of interest.” However, would having this isotype info actually change the clinical management of anaphylaxis or subsequent dosing strategy? Recommendation to acknowledge that isotyping is not typically required to manage this.

Lines 126-129: Sentence needs re-structuring for clarity.

131

2. Cytokine Release Syndrome Comment on CRS Section: Recommendation to clarify inclusion of CRS in this document. The TGN1412 case was NOT due to an immune reaction, as such, but part of the efficacy and mechanism of action of the molecule. Proper dose escalation could have prevented the case. Perhaps the mechanism described in the Appendix should be moved to this section.

133 - 139

Lines 131-138: Cytokine release syndrome is generally not related to ADA. For example, the TeGenero issue was due to immune over-stimulation by the drug itself and not due to immunogenicity. There can be a theoretical concern for agonistic biological drugs that ADA could cross-link receptor bound drug molecules and cause super-agonistic reactions, possibly leading to cytokine release syndrome. The Agency must be more specific in this section.

Lines 137-139: The document should clarify if this is required for therapeutics whose

underlying biology may trigger cytokine modulation.

141

3. “Infusion Reactions” Line 141: The title should state “Infusion and injection-site reactions” unless the Agency is specifically excluding ‘injection-site reaction’ that can occur as a dermatologic reaction after subcutaneous administration of biologic drugs.

Line 141: See comment on Line 131 - Infusion reactions may have little to do with

"Immunogenicity." Classification of infusion reactions would be helpful in this section.

143 - 154

Lines 148-150: Details or examples of how to report these adverse reactions should be provided.

Lines 150-152: It is unclear if this request is immediately after dose administration, any time after dose administration or immediately following an “infusion reaction”. Suggest modifying sentence to clarify. Is this feasible to implement?

156

4. Non-acute Reactions

158 - 167

Lines 163-165: the clinical signs listed (fever, rash, arthralgia, etc) are often used to describe infusion reactions. The Agency should reconsider whether these should be described as “Non-acute reactions” (section 4) or whether these should be included in section 3 as infusion reactions.

Lines 166-167: While circulating immune complexes are a theoretical concern, are they

ever/often driven by immunogenicity in clinical trials? Lines 163-167: Do clinical signs including fever, rash, etc. require immune complex testing?

Is this drug-specific immune complex or is a general clinical test recommended?

169

5. Cross-Reactivity to Endogenous Proteins

171 - 177

179 - 186

Lines 179-186: Breast milk has been shown not to contribute meaningfully to the antibody exposure to the infant. Exposure is through utero, not breast milk. Recommend changing text to “…resulting from antibodies to the therapeutic protein counterpart may potentially negatively impact fetal or neonatal development when such responses are generated during pregnancy.

189 - 191

IV. RECOMMENDATIONS FOR IMMUNOGENICITY RISK MITIGATION IN THE CLINICAL PHASE OF DEVELOPMENT OF THERAPEUTIC PROTEIN PRODUCTS

193 - 198

200 - 201

203

205 - 210

Line 207: Proposed change: “…develop and implement sensitive, qualified or validated assays

Rationale: Within the Bioanalytical community, a “qualified” assay has come to mean something less than a “validated” assay. Suggestion is to either delete “qualified” or to add “validated.” This is consistent with language in the 2009 draft guidance for Assay Development.

…”

Lines 207-208: Recommend including “bioassays for neutralizing antibodies” in sentence describing the need for sensitive assays. Lines 208-210: In some cases, assay validation of drug tolerance is sufficient to exclude the necessity of taking concomitant samples for drug level determinations. Recommend adding “unless assay validation obviates this need” to end of the sentence. Line 210: Specify if this refers to only the drug substance, or if in CMC parlance, this may

include the constituents of the formulation (i.e., excipients) if they are potentially immunogenic as well (ADA or ATA). For clarity, a section should distinguish immunogenicity due to the drug product (drug substance + excipients) from immunogenicity due to the drug substance.

212

214 - 221

Line 214: Suggestion to add “and post-baseline

sampling...”

Line 216: Sampling that is too frequent can increase the untreated positive rate of a study. Line 216-218: Do "early" and "prolonged" refer to parts within a clinical development

program, or to points within an individual clinical trial? Please clarify. Lines 219-221: “whether antibody responses are transient, whether a neutralizing antibody

response has developed, and whether these responses are associated with long-term clinical sequelae” could be taken to mean that Nab are persistent antibodies. It is important that the kinetics of ADA (transient or persistent antibodies) versus neutralizing and non-neutralizing antibodies be considered as separate attributes of immunogenicity. Such statements should be clarified to avoid misunderstanding.

Line 219: Please provide some definition of “transient.” Proposed change to Line 221: “these responses are associated with long-term clinical

sequelae. Please add: “It is key that antibody blood samples are drawn before administration of a therapeutic protein.

Rationale: A sample blood draw should be taken before drug is administered to ensure all of the drug is delivered.

Line 223-225: In addition to unscheduled samples, samples from early terminations should also be collected for immunogenicity assessment.

223 - 225

Lines 223-225: It is helpful to collect samples at a premature termination visit. Timing of sample analysis should also be carefully considered. Analysis of study samples periodically in batches (e.g. quarterly) may be preferable to analysis of all study samples only after a clinical study is completed.

227 - 228

Line 227-228: Please provide guidance on how long these sample should be stored. Lines 227-236: Differentiation between medication/molecules enhancing the immune

response due to activating by system (i.e. the cytokine release) and blocking/neutralizing molecules is necessary.

230

232 - 241

Lines 232-241: It is not correct that SC application is more immunogenic. There are several case studies which also show the opposite or equivalence.

Lines 239-240: Too vague. The team should suggest what circumstances would require a conservative approach to FIH trial design. Lines 232-241: what’s the relevance of the “Dosing section” to immunogenicity assessment?

243 - 248

250

252 - 257

Lines 252-253: Please define “low titer” and “high titer.” The phrase “high antibody titers” is quite subjective and might change from one project to another one.

Line 254: Please add “In certain "high risk"

situations...

259 - 263

Lines 259-263: Is this to be done with banked samples retrospectively as an exploratory assessment in the absence of anticipation and planned analysis? How are the exploratory data to be used other than for exploratory purposes and the acquisition of information to refine future clinical development and/or mitigation strategies? Line 259: Please define or add examples of “clinically relevant immune responses.”

265 - 269

Line 265: Please add “In some "high risk"

cases...”

271

273 - 277

Lines 273-277: Pre-specified criteria for acceptable immunogenicity differences is subjective. Recommend providing examples of pre-specified criteria (and statistical methods) that would be used to determine acceptability. Lines 273-277: regarding justifying “what differences in incidence or severity of immune responses would constitute an unacceptable difference in product safety”. By default, most differences should be considered unacceptable with higher risk products. The sponsor should instead justify what differences would not constitute an unacceptable level. Line 277: The same anti-therapeutic antibody assay must be used to enable valid comparisons.

279

281 - 289

292 - 293

V. PATIENT- AND PRODUCT-SPECIFIC FACTORS THAT AFFECT IMMUNOGENICITY

295

A. Patient-Specific Factors That Affect Immunogenicity

297 - 299

Line 297-299: The statement of “caution” is unclear. The Agency should advise what type of caution can be taken when moving from one patient population to another.

301

1. Immunologic Status and Competence of the Patient

303 - 315

Lines 304-307: The GCSF statistics are compelling and the point is clear, but it might be worthwhile to add a qualifying statement about the number of patients (n=28 total), the dosing conditions and how immune-suppression may or may not be applied for various patient populations. Since GCSF has an endogenous counterpart, it would be of interest to also address the safety aspect of cross-neutralization of endogenous counterpart.

Line 304: Request agency to provide a reference to support statement, “For example, 95

percent of immune-competent cancer patients generated neutralizing antibody to a Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) product, but only 10 percent of immune-compromised cancer patients did so (Ragnhammar, et al. 1994).”

Line 312-313: References should be provided to justify generational effects on ADA

induction. Line 313: Please provide an example of what a "particular caution" should be. Line 315: The Stebbings reference is related to a cytokine storm event upon first

administration of a therapeutic. This was not driven by an unwanted immune response.

317

319 - 320

Lines 319-320: This statement is very vague. Should a rationale be based on the anticipated immunogenicity risk or the anticipated immunocompetence level of the population?

Line 319-320: The recommendation is relevant for FIH. Not specifically for immunogenicity.

322

2. Prior Sensitization /History of Allergy

324 - 327

329 - 332

334

336 - 337

339

3. Route of Administration, Dose, and Frequency of Administration

341 - 351

Lines 341-351: Are these statements still considered accurate with the increased number of antibodies in the clinic? A newer and more widely available reference would be appropriate.

353

355 - 357

359 - 361

363

4. Genetic Status

365 - 370

Lines 367-370: This HLA mapping recommendation should be for high risk products, but probably not necessary for lower risk products.

372

374 - 379

Lines 374-379: It would be useful to cite relevant literature on HLA haplotype in addition to the Hoffman 2008 paper, either a similar study with comparable results or another case study.

Line 379: Does this suggest that MS patients be HLA haplotyped if a new IFN-beta

therapeutic is being administered to them, and so on? Please clarify.

381

5. Status of Immune Tolerance to Endogenous Protein

383 - 389

391 - 402

Line 401: It would be good to discuss whether there are cases where prior exposure to a similar product has resulted in tolerization.

404

406 - 409

Lines 406-409: How is this information to be used to help mitigate immune responses? Please provide clarity.

411 - 413

Lines 411-413: It is not clear what would be gained by gathering information on the level of the endogenous protein to the risk assessment. A statement on what this should be used for would be helpful. Referencing some of the newer risk assessment publications would also be helpful for this section.

415 -416

418 - 421

423

425 - 427

429 - 431

Line 429: Are they suggesting that MS patients be HLA haplotyped if a new IFN-beta therapeutic is being administered to them, and so on?

Lines 429-431: Would this then be applied to a risk-mitigate approach on the frequency axis

or would genetic screening be implemented? Are there cases of genetic screening for polymorphisms that could be cited here; perhaps move lines 439-442 up to this section? excluding genetic deficiency syndrome, i.e. growth hormone deficient, etc...

434

B. Product-Specific Factors That Affect Immunogenicity

436

1. Product Origin (foreign or endogenous)

438 - 450

Lines 438-450: The guidance has correctly identified product-specific factors that affect immunogenicity. However, it should explicity state that immunogenicity testing should be considered when changes are made to any of these factors, such as primary container closure system, route of administration, etc., particularly in a post-approval setting.

Lines 447-450: Are there examples of tolerance to bacterial or pathogenic proteins due to

chronic exposure?

452 - 459

Line 452: This caveat is also true of synthetically generated peptides, which can contain premature termination products, adducts, etc.

Lines 457-459: Suggested evaluation of the risk posted by immune responses to any known

protein or other impurities that may be present in the product is too broad. It is not clear whether any impurities, even those present at trace amounts, need to be investigated.

Lines 457-459: Suggestion to clarify that impurities that have known risk of immunogenicity

induction or otherwise should be evaluated. Lines 457-459: Does this mean to deliberately look for HCP antibodies?

461

463 - 465

Line 463-465: Regarding process and product related impurities it is advised that the Agency specifically advise that products derived from human cell lines be particularly considered for immunogenicity risk assessment, and the top few impurities be specifically identified by the sponsor as there may be unintended consequences due to ADA cross-reactivity with endogenous proteins.

467

2. Primary Molecular Structure/Post Translational Modifications

469 - 477

Lines 474-477: This does not generally seem to be a problem for allotypic variants of IgGs.

479 - 494

Lines 491-494: The reference is for a highly unusual fusion protein and not representative of the bulk of fusion proteins which utilize Fc. Recommend updating this comment with more recent information.

496 - 507

509

511 - 513

Lines 511-513: Is this true for Fc fusions? Is it recommended to always develop an anti-Fc domain mapping assay in this case?

515 - 519

Lines 515-519: Is domain specificity always necessary or helpful?

521 - 526

Lines 521-526: Is this an explicit recommendation that manufacturers purify and obtain therapeutics from animal samples to test for these modifications.

Lines 521-526: Do we need to do this for all monoclonal antibodies?

528

3. Quaternary Structure: Product Aggregates and Measurement of Aggregates

Lines 528-588: This section discusses risk associated with molecular properties, and as part of this controlling aggregate to as low an amount as possible, but does not include any mention of direct assessment of risk in predictive assays, or the ability to use this information in ranking potential risk of modifications and aggregates. The agency should comment on the ability to decrease risk assessment based on these types of assessment. The document should address the ability to use risk assessment based on in vitro or in vivo data, demonstration that the attribute is found in circulation, etc to prioritize resources and focus comparability studies etc on the attributes with the highest associated risk. For instance if the relative risk of immunogenicity for oxidation of a particular protein is lower than others, does that increase the range allowed in that product?

530 - 537

Lines 531-537: The references do not provide sufficient support for the described mechanisms. Seong and Matzinger 2004 is an opinion paper where the hypothesis that hydrophobic patches on aggregated proteins can serve as signals to activate the immune system is described. However, no experimental evidence to the latter is available. Both studies Dintzis, et al. 1989 and Bachmann, et al. 1993, as well as the review Bachmann and Zinkernagel 1997, show that antigen density/organization may influence B cell responses. However, none show experimental evidence for a specific mechanism (e.g. receptor cross-linking) by which this may happen.

Therefore, we suggest wording changes to reflect the lack of clarity regarding the mechanisms by which aggregates may activate the immune system. In addition, alternative references need to be provided.

Proposed change (if any): “Potential mechanisms by which protein aggregates may facilitate immune responses could include the following: extensive cross-linking of B cell receptors, causing efficient B cell activation (ref. needed); enhancing antigen uptake, processing, and presentation; and triggering immunostimulatory danger signals (ref needed), thus recruiting the T cell help needed for generation of high-affinity, isotype-switched IgG antibody, the antibody response most often associated with neutralization of product efficacy (ref needed).

539 - 546

548 - 563

Lines 548-552: The reference provided is inadequate. Bachmann, et al. 1993 presents results using glycoprotein of the vesicular stomatitis virus serotype Indiana [VSV-G (IND), which may or may not have the general applicability suggested in this sentence. We suggest that alternative or additional references are provided.

Lines 557-561: The sentence contains two statements. However, all references in it pertain

to the second one. We suggest splitting this sentence in two and providing an appropriate reference for the first statement.

565

567 - 573

575 - 581

Lines 575-588: The discussion clearly indicates that the highest risk is associated with aggregate in the 2-10 micron range, but the assays mentioned are useful for dimers and oligomers in the nanometer range, while none of the methods that are useful for the aggregates of concern are included. Suggest deleting the list of analytical methods included, and instead switching the emphasis to the methods that are applicable to the species of greatest risk, such as Light obscurtion, flow microscopy, Coulter counter, etc.

583 - 588

Line 583-584: Sentence needs clarification.

590

4. Glycosylation/Pegylation

592 - 604

Lines 597-598: Is this true for monoclonal antibodies? Line 603: The Liu reference does not address loss of efficacy or safety consequences;

perhaps additional references might be helpful. Lines 599-604: If anti-PEG antibodies are suspected, it would be very useful to ensure that

the antibody detection method is capable of detecting IgM antibodies. Line 593-594: regarding “shielding immunogenic protein epitopes from the immune system”

– this is true for B cells and antibodies (humoral immune system) alone. T cells are not shielded from recognizing glycosylated proteins because they recognize processed peptides.

606

608 - 610

Lines 608-610: Suggested rewording to “For proteins that are normally glycosylated, use of a cell substrate production system that glycosylates the protein in a nonimmunogenic manner and does not deviate greatly from the normal glycan repertoire is recommended.”

612 - 613

Lines 612-613: Is the assessment for anti-PEG antibodies always necessary or might a subset population analysis be sufficient? For example, if there are no (potentially) ADA related AE or PK abnormalities and sufficient efficacy, how is this characterization to be used?

615

5. Impurities with Adjuvant Activity

617 - 625

Lines 617-625: Section is very vague on how to justify safe levels of beta-glucan. Request for Agency to provide clarity on CHO-protein and recommend what to do with data, as well as provide additional references for which levels of these have been problematic.

627

629 - 631

Lines 630-631: Since IIRMIs can apparently synergize (Verthelyi & Wang), how can meaningful limits be set? Would it be helpful to add approximate levels of clinically relevant IIRMIs to inform assay development? Alternatively, citation to relevant literature could be useful.

Lines 629-631: This paragraph appears to be addressing CMC attributes while the sentence

below (Lines 633-634) appears to be addressing bioanalytical and pharmacological attributes. It might be helpful to add more detail to lines 633-634 to demonstrate this differentiation. Examples or citations of biomarkers used for this end might also be helpful.

Lines 629-631: Is the evaluation of IIRMIs required for all products? Or should this be done

when the immunogenicity-related safety concerns arise?

633 - 634

Lines 633-634: The intent of this sentence is unclear. What kind of biomarkers can be used? Please give examples. Also, explain how these might be used to enable limit setting.

636

6. Immunomodulatory Properties of the Therapeutic Protein Product

638 - 649

651

653 - 655

657 - 659

661

7. Formulation

663 - 675

677 – 680

682

684 - 687

689 - 693

695

8. Container Closure Considerations

697 - 702

704 - 705

707 - 709

711 - 712

714 - 716

718 - 722

724 - 730

732

734 - 737

739 – 742

744 - 748

750

9. Product Custody

752 - 754

756 - 758

760 - 762

Suggested change to Line 761: “For example, the storage of epoetin-alpha

under inappropriate conditions by unauthorized vendors…”

764

766 - 770

773

VI. CONCLUSION

775 - 784

787

VII. REFERENCES

789 - 1000

1003

VIII. APPENDIX

1005

A. Diagnosis of Anaphylaxis

1007 - 1008

1010 - 1016

1018 - 1026

1028 - 1033

1035 - 1036

1039

1041 - 1050

1052 - 1060

Lines 1052-1060: A clinical lab/ FDA / industry collaboration has produced a guidance document on IgE measurements specific for therapeutic proteins. Recommend adding and discussing the CLSI reference document: Design and Validation of Immunoassays for Assessment of Human Allergenicity of New Biotherapeutic Drugs. Clinical and Laboratory Standards Institute Guidance Document I/LA-34P.

1062 - 1067

1069 - 1075

1077 - 1095

1097 - 1103

1106

B. Cytokine Release Syndrome

1108 - 1118

Lines 1108- 1118: Although a number of in vitro methods claim to predict the likelihood of cytokine release syndrome in vivo, these methods have not been standardized and they yield highly variable data. A HESI/ILSI initiative may help standardize but at the moment data from such methods is unlikely to have much predictive utility. Since CRS can occur at first dose, it is unlikely to be consistently associated with unwanted immune responses to therapeutic proteins.

1120 - 1141

1144

C. Non-Acute Immune Responses

1146 - 1159

1161 - 1165

1168

D. Antibody Responses to Therapeutic Proteins

1170 - 1182

Line 1170: Proposed change: Antibodies to therapeutic proteins may be classified as either binding to functional domain or non-functional domain of the therapeutic protein.

Line 1181: Proposed change: “…and facilitation of epitope spreading and generation of anti-

idiotypic antibodies, allowing the emergence …”

1184 - 1199

1201 - 1203

Lines 1201-1203: It might be helpful to provide examples of monoclonal antibody “loss of efficacy” case studies along with recourse.

1205 - 1217

1219 - 1223

Line 1219: What kinds of circumstances? Please elaborate. Lines 1219-1231: Some patients continue to have low levels of antibodies for many years. Recommend adding a length of time (suggest 1 year) to follow subjects that are antibody positive in cases where they never return to baseline. Lines 1221-1223: Should an assessment take place for all therapeutic proteins or just under

special circumstances? If so, what are these situations?

1225 - 1232

1235

E. Utility Of Animal Studies

1237 - 1252

Lines 1251-1252: Same as above, breast milk has been shown not to contribute meaningfully to the antibody exposure to the infant. Exposure is through utero, not breast milk. Recommend removing sentence.

1254 - 1259

1262

F. Comparative Immunogenicity Studies

1264 - 1272

1274 - 1276

1278 - 1280